>> reporter: good evening, diane, from rome, where secretary of defense leon panetta is urgently trying to get more information about this attack on americans and others. three americans are believed to be held hostage right now, but u.s. officials warn that number is fluid. secretary panetta tonight says the u.s. will take all necessary steps to deal with this crisis. >> by all indications, this is a terrorist act. and the united states strongly condemns these kinds of terrorist acts. it is a very serious matter when americans are taken hostage along with others. >> reporter: it all began when 20 armed islamic militants, believed to be affiliated with al qaeda, approached a group of oil workers. the attackers were reportedly heavily armed, driving in three unmarked vehicles. the oil workers were on a bus headed to a nearby airport. there was a fight -- security forces for the workers battled back. when the smoke cleared, at least one foreign worker was dead, others wounded. the terrorists then headed to the compound where the gas refinery workers live. while it is unclear how many fore